The long-term objective is to use an invertebrate animal model, the marine mollusc Aplysia californica, to understand the neural basis of environmental regulation of seasonal fluctuations in reproductive activity. Because of their relatively simple nervous system, Aplysia have been widely used for molecular and electrophysiological investigations of the neuroendocrine control of egg laying behavior. However, there is little information on how the environment regulates the timing of this behavior. Recent work from our laboratory suggest that both photoperiod and temperature regulate egg laying. A broad aim of the proposed work is to locate and to study components of the pathway(s) by which photoperiod and temperature have their effects on reproductive behavior. The specific aims of this proposal are: 1) To determine whether the eyes mediate effects of photoperiod on egg laying behavior; 2) To determine the neural and/or hormonal mechanisms by which photoperiod affects egg laying behavior; 3) To determine the neural and/or hormonal mechanisms by which temperature affects egg laying behavior, 4) To explore the strong seasonal suppression of spontaneous egg laying behavior in the winter and spring. The proposed work will apply cellular, endocrinological and electrophysiological techniques to study the effects of photoperiod and temperature on the neuronal components important in egg laying. Initial studies will employ an in vivo electrical recording technique in behaving animals to determine which tissues are responsive to photoperiod and temperature. Once this is accomplished, the nervous system can be removed and placed in culture to explore the cellular responses to the two environmental variables. Furthermore, measurement of known hormones involved in the egg laying process will allow an additional evaluation of the cellular processes underlying environmental regulation of reproduction. Behavior is a function of interactions between the brain and the environment. The proposed studies will provide a novel approach to the understanding of cellular mechanisms which underlie reproductive behavioral responses to environmental variables. Furthermore, these investigations will enhance our knowledge of the neuroendocrine control of both activation and suppression of fertility.